Snow falls more lopsided from town to town
Less than 30 miles separate Mundelein from O'Hare International Airport, and yet the Lake County suburb was pummeled by an 8.2-inch snowfall while plows removed just 2.6 inches from the airport runways.
The discrepancy grows even more south of Chicago, where communities such as Joliet and Orland Hills saw barely a dusting Thursday night into Friday morning.
But the lopsided snowfall, which dropped this season from fifth to seventh least snowy on record, isn't typical.
National Weather Service meteorologists Matt Friedlein and Charles Mott looked at the past 30 years and found that the north metropolitan area annually averages just a couple inches more of snow than its southern counterpart.
“Event to event, and winter to winter, you may see a difference,” Friedlein said. “But over time, it all seems to average out.”
Despite the most recent storm, snowfall totals this winter remain fairly consistent throughout the region.
Friedlein said Romeoville, the site of the weather agency's regional office, has recorded 19.6 inches of total snow through Friday, or the same as O'Hare. A reporting station near Midway Airport has recorded 20.8 inches of snow. That's more than far Northwest suburban Harvard's 20.5 inches and less than Barrington's 21.8 inches.
Those totals are still well below normal, according to Jim Angel, state climatologist for the Illinois State Water Survey.
Using reports from Midway — the region's longest-serving weather station dating back to 1928 — this season now ranks as the seventh least snowy on record. Midway has seen 20.2 inches total, down from a normal of 37.1 inches.
While the Northernmost suburbs may average slightly more snow, winter precipitation totals are slightly higher in the south. Rain there is usually slower to convert to snow due to warmer temperatures.
Looking ahead, the entire region will likely see both above-average temperatures and precipitation in the next three months, according to weather models.
“We're looking for it to be wetter and more mild than normal,” Friedlein said.
One reason the Chicago area has experienced such a mild winter season is that the region currently is experiencing positive phases of a large-scale phenomenon known as the North Atlantic Oscillation and the Arctic Oscillation. They cause stronger westerly upper level jet streams, which block cold air from spilling southward.
The past two winters experienced atmospheric pressure trends mostly in the negative phase, leading to cold and snowy conditions.